Conversion of hydrocarbon oils



Dec. 22, 1936. l.. c. HUFF CONVERSION OF HYDROCARBON OILS Original FiledJan. 2, 1951 INVENTOR LYMAN c. HUFF BY y( ATTORNE Patented Dec. 22, 1936UNlTED STATES TE'l FEE assignments, to Universal Oil Products Company,Chicago, Ill., a corporation of Delaware Application January 2, 1931,Serial No. 506,136

BEISSU Renewed March 4, 1936 4 Claims.

This invention relates to an improved process and apparatus for treatinghydrocarbon oils, and refers more particularly to the conversion ofrelatively heavy oils into lighter and more valuable 5 products.

The invention may comprise the employment of aprimary cracking systemwherein relatively mild conversion conditions may exist and throughwhich oil may pass, and a secondary cracking system wherein more severeconversion conditions may be maintained. Raw oil charging stock may besupplied to a heating element of a primary cracking system, and refluxcondensate from a fractionator of said system may be returned to saidprimary heating element for reconversion. Vapors from a fractionator ofsaid primary cracking system m-ay be subjected to further fractionationin a secondary fractionator of said system, and reflux condensate fromsaid secondary fractionator may be supplied to a heating element withina second-ary cracking system. Vapors, from a reaction chamber of saidsecondary cracking system may be subjected to fractionation in aseparate fractionator of said system, while reflux condensate from s-aidsystem and fractionator may be returned for reconversion, either to theprimary cracking system or to the secondary cracking system, or, inpart, to both.

As a particular feature of the invention, a secondary charging stock,such, for example, as bottoms from the redistill-ation of a crackeddistillate, the bottoms from a secondary tower of a separate crackingsystem, or other oil, preferably similar in characteristics to refluxcondensate from a secondary fractionator of a primary cracking system,may be fed toa secondary cracking system for conversion, and suppliedeither overhead to a fractionator of said system, to a secondaryfractionator of a primary cracking system directly into the inlet sideof a secondary heating element, or into a stream of heated productsbeing discharged from said secondary heating element, or partially toboth.

As another feature of the invention, vapors from a reaction chamber of asecondary cracking system may be employed to reboil reflux condensate ina secondary fractionator of a primary cracking system, by passing saidvapors into indirect contact therewith, prior to their introduction intoa fractionator of the secondary cracking system.

l As another feature of the invention, a portion of either the primaryor secondary charging stock, or both, may be blended with the residualoil withdrawn from a reaction chamber of a second-ary cracking system toimprove the quality of the latter.

Other and further objects and advantages of the invention Will becomeapparent from the 5 following description and drawing, showing adiagrammatic, side-elevational View of one form of apparatus in whichthe invention m-ay be carried out.

Referring to the drawing, raw oil charging stock may be supplied througha line I, controlled by a valve 2, to a pump 3, from which it may passthrough a line 4, controlled by a valve 5, to a primary fractionator 6,where it may assist in fractionating the vapors undergoing treatmenttherein, and being discharged from said fractionator, together with therelatively heavy, condensed components of said vapors, through a line 1,controlled by a valve 8, to a pump 9, from whence said oil and condensedcomponents may 20 be fed through a line I0, controlled by a valve I I,to a primary heating element I2. All or any desired portion of said rawoil may pass from pump 3 through a line I3, to a line I4, controlled bya valve I5, communicating with said line I9, and passing through saidlatter line directly to heating element I2.

Primary heating element l2 may be disposed in any suitable type offurnace I6, and the oil passing therethrough may be heated to anydesired conversion temperature under any desired pressure, after whichit may pass through a line I'I, controlled by a valve I8, to a primaryreaction chamber I9, wherein separation of vapors and unvaporizedmaterial may occur. In event the primary cracking system be operated forthe production of a liquid residual product, said residue may be removedfrom chamber I9 through a line 20, controlled by a valve 2|. Shouldnonresiduum operations be employed, coke or carbonaceous materials maybe allowed to accumulate in primary reaction chamber I9 and removedtherefrom after operations are discontinued.

Vapors from chamber I9 may pass through a line 22, controlled by a valve23, to primary fractionator 6, wherein their relatively heavy,insufficiently converted components may be condensed and returned forreconversion in primary heating element I2, as already described. Vaporsfrom said fractionator 6 may pass through a line 21, controlled by avalve 28, to a secondary fractionator 29, of the primary system, wherethey may be subjected to further fractionation for separation of thelight components, preferably falling within the boiling range of motorfuel. The lighter components of said vapors may pass from saidfractionator through a line 36, controlled by a valve 3l, to a primarycondenser 32 for condensation and cooling. Condensed distillate andincondensable gases may pass from said condenser 32 through` a line 33,controlled by -a valve 34, to a primary receiver 35. Incondensable gasesmay be released from said receiver through a line 36, controlled by avalve 31, while distillate may be removed from said receiver through aline 38, controlled by a valve 39.

Relatively heavy components of the vapors subjected to additionalfractionation Within secondary-fractionator 2.9 of the primary system,may pass from l'said 'fractionator through a line 40, controlled by avalve 4I, to a pump 42, from which they may be fed, via a line 43, intoa line 44, controlled by a valve 45, and thence through a line 46 into asecondary heating element 41 of a secondary system. Secondary heatingelement 41 may be disposed within any conventional type of furnace 48,and oil passing therethrough may be subjected to any desired conversionconditions, preferably of a more severe order than that maintained inprimary heating element I2, After subjection to the necessary conversionconditions within heating element 41, the heated products may bedischarged from said element through a line 49, controlled by a valve59, and passed into a secondary reaction chamber 5I, of the secondarysystem. Vapors may be withdrawn from said secondary reaction chamber 5Ithrough a line 52, controlled by a valve 53, and passed through areboiler 54 suitably disposed within secondary fractionator 29, fromwhich they may pass through aline 55, to a fractionator 56 of thesecondary system. By providing a reboiler 54 Within said secondaryfractionator 29, the reflux condensate within said fractionator may beheated by indirect contact with the relatively hot vapors passingtherethrough from said second secondary reaction chamber 5I, eiiecting asub.- stantial stripping of entrained desirable light products from saidreflux before its subjection to reconversion in secondary heatingelement 41,

Lighter vapors may be removed from said fractionator 56 through a line51, controlled by a valve 58, and may be passed to a condenser 59 of thesecondary system, wherein they may be subjected to condensation andcooling, the condensed distillate and incondensable gases passing fromsaid condenser through a line 6i), controlled by a valve 6|, to asecondary receiver 62. Incondensable gases may be released from receiver62 through a' line 63, controlled by a valve 54, and condenseddistillate may be withdrawn from said receiver through a line 65,controlled by a valve 66. If desired, instead of passing to separatecondensation, cooling and collecting, vapors from fractionator 56 may bediverted, wholly or partly, through a line 24, communicating with line51, (line 24 being controlled by a valve 25), and passing through saidline 24 into secondary fractionator 29 for further fractionation,together with the vapors from primary fractionator 6.

It will be understood, of course, that the usual expediente forcontrolling the outlet temperature of the vapors from variousfractionators of the system, such as recirculating a portion of the nalproducts from receiver 62 and/or receiver 35, may be adopted, althoughnot shown in detail herein.

Reflux condensate from fractionator 56 of the secondary system, may beWithdrawn through a line 61, controlled by a valve 68, and passed to apump 69, from whence it may be passed through a line 16, controlled by avalve 1|, and line I0, into primary heating element I2 for reconversion;or any desired portion of said reflux, instead of passing directly toheating element I2, may be introduced into primary fractionator 6through a line 12, controlled by a valve 13, communicating With saidline 16, and further assist in fractionation of the vapors undergoingtreatment within said fractionator, after which it may pass, togetherwith the heavier condensed portions of said vapors within ractionator 6and raW oil charging stock to said primary heating element I2, throughline 1, pump 9, and line Il), as previously described. Instead of beingreturned to said primary heating element l2, reflux condensate from saidfractionator 56 may pass, either Wholly or partly, from line 16, throughwhich it may be discharged, into line 44 and through control valve 14interposed in said line 44, and thence into line 46 to heating element41 of the secondary system for reconversion at an elevated temperature;or, instead of passing to secondary heating element 41, said reflux may,if desired, pass from line 44 through a line 15, controlled by a valve16, into secondary fractio-nator 29, combining therein with refluxcondensate formed in said fractionator, and thence passing therewiththrough said line 49, pump 42, lines 43, 44

and 46 to heating element 41, as previously described. It will beunderstood, of course, that in event secondary fractionator 29 beoperated at a lower pressure than that employed in fractionator 56, anydesired portion of reux condensate from fractionator 56 may passdirectly therefrom to fractionator 29 through line 61 and thence througha line 11, controlled by a valve 18, and line 15, in which event pump 69may be eliminated.

A secondary charging stock, preferably similar in characteristics to thereux condensate from secondary fractionator 29, or, in event refluxcondensate from fractionator 56 is also returned to secondary heatingelement 41, similar in characteristics to the combined reflux from bothfractionators, may be supplied through a line 19, controlled by a valve80, to a pump 8 I, from which it may be fed through a line 82,controlled by a valve 83, and a valve 84, and line 46, communieatingwith said line 82, directly to said secondary heating element 41; orthrough a line 85, controlled by a valve 86, and a line 81, controlledby a valve 86, to secondary fractionator 29; or through said line 85 andcontrol valve 89 interposed in said line, to fractionator 56; orpartially to either or all of said elements. A portion or all of saidsecondary charging stock may be fed through pump 3| line 82 and a line99, controlled by a valve 9|, into line 49 through which the reconvertedproducts may discharge from heating element 41, to contact directly andcommingle with said stream of heated products, serving to cool saidstream to any desired temperature prior to its entrance into secondaryreaction chamber 5I.

Unvaporized residual oil from secondary reaction chamber 5I may bewithdrawn through a line 92, controlled by a valve 93, and passed tostorage or elsewhere. A portion of raw oil frompump 3 may be passedthrough line I3, and thence through valve 98, interposed in said line,and introduced into a line 94, controlled by a valve 95, to blend inline 92 with the residual products being withdrawn from secondaryreaction chamber 5l. Similarly, any desired portion of the secondarycharging stock from pump 8i may be passed through line 82, valve 83,line 96, valve 91, line 94, and valve 95, into line 92 to commingle Withsaid residual products.

Pressures employed in both the primary and secondary cracking elementsof the system may range from sub-atmospheric tosuperatmosphericpressures as high as 2000 pounds per square inch or more. Substantiallyequalized pressures may be employed throughout the entire process, ordifferential pressures may be employed between various elements thereof.Preferably, milder conversion conditions may be employed in the primaryheating element than in the secondary heating element. Conversiontemperatures employed may range from 750 F., to 1200 F., more or less.

As a specic example of one operation of the process, and the resultsobtainable thereby, a primary charging stock having approximately a 22A. P. I. gravity, and representing approximately 75% of the totalcharge, and a secondary charging stock, amounting to about 25% of thetotal charge, being the pressure distillate bottoms from aredistillation of cracked distillate, and somewhat similar incharacteristics to reflux condensate from the secondary fractionator ofthe primary cracking system, is subjected to treatment at a temperatureof about 910 F., and a pressure of about 200 pounds per square inch in aprimary heating element. This pressure is substantially equalized in theprimary reaction chamber and primary fractionator. A temperature ofabout 1050" F., and a pressure of about 100 pounds per square inch ismaintained in a secondary heating element, and this temperature isreduced by the introduction of a portion of the secondary charging stockat substantially the point of outlet of said secondary heating element,to a temperature of about 925 F. The secondary reaction chamber,fractionator, and secondary condensing and collecting equipment may bemaintained under a substantially equalized pressure of about 30 poundsper square inch. The secondary fractionator and succeeding condensingand collecting equipment of the primary system may be maintained under apressure of about 60 pounds per square inch, and a nonresiduum operationis employed in the primary system.

As a result, a yield, based on the total ravv oil supplied to theprocess, of approximately 63% of motor fuel, having an anti-knockquality substantially equivalent to a blend of 50% benzol and 50%Pennsylvania straight-run Pennsylvania gasoline may be obtained. About14% of residual oil, suitable for sale as fuel, and about 55 pounds ofcoke per barrel of oil charged may also be obtained; the only otherproduct produced may be a gas of high caloric value.

I claim as my invention:-

l. A conversion process which comprises subjecting hydrocarbon oil tocracking conditions of temperature and pressure in a primary zone,simultaneously cracking a lighter oil at higher temperature in asecondary cracking Zone, subjecting the vapors evolved in said zones toindependent primary fractionation in separate fractionating zones andsupplying reflux condensate thus formed in said separate fractionatingzones to said primary zone, then combining the separately fractionatedvapors and subjecting the saine to common secondary fractionation,supplying resultant secondary reflux condensate to said secondarycracking zone, and finally condensing the vapors uncondensed by saidcommon secondary fractionation.

2. The process as defined in claim 1 further characterized in that thevapors evolved in saidI secondary cracking zone, prior to the primaryfractionation thereof, are passed in indirect heat exchange with saidsecondary reflux condensate to reboil the latter before introduction ofsaid secondary reflux condensate to the secondary cracking zone.

3. A conversion process which comprises subjecting hydrocarbon oil tocracking conditions of temperature and pressure in a primary zone,simultaneously cracking a lighter oil at higher temperature in asecondary cracking Zone, subjecting the vapors evolved in said zones toindependent primary fractionation in separate fractionating zones andsupplying reflux condensate thus formed in said separate fractionatingZones to said primary zone, then combining the separately fractionatedvapors and subjecting the same to common secondary fractionation,supplying resultant secondary reflux condensate to said secondarycracking zone, and finally condensing the vapors uncondensed by saidcommon secondary fractionation.

4. The process as defined in claim 3 further characterized in that thevapors evolved in said secondary cracking Zone, prior to the primaryfractionation thereof, are passed in indirect heat exchange with saidsecondary reiiux condensate to reboil the latter before introduction ofsaid secondary reflux condensate to the secondary cracking zone.

LYMAN C. HUFF.

